A winter fog study in the offing


Winter in the Hindu Kush Himalayas usually lasts from December to February. During this time many low-land areas and valleys experience short durations of morning fog.  Since the 1990s, however, big changes have been observed across the Indo-Gangetic Plains stretching from Pakistan across northern India and southern Nepal and Bhutan to Bangladesh, with periods of dense fog and low stratus clouds stretching across vast regions continuously for weeks.  This persistent winter fog has many adverse impacts: low visibility, impairing surface and air transport; lack of sunlight, affecting crops; low temperatures and reduced ventilation of air pollutants, affecting people’s health, especially of the poorest who are least able to protect themselves. 

Therefore, atmospheric scientists from the five countries of Pakistan, Bangladesh, Bhutan, India, and Nepal have partnered with ICIMOD to carry out a comprehensive interdisciplinary regional study in these countries. They will use four different approaches for the study: surface atmospheric measurements, remote sensing, atmospheric modelling, and social science research.  While pilot studies were carried out in the winter of 2014-2015, a full-scale study has been scheduled for the 2015-2016 winter.  

The study is expected to lead to a regional scale understanding of mechanisms behind the formation of the persistent winter fog, its impacts on people, and possible mitigation measures. Today, there are gaps in the scientific understanding of the relative role played by moisture available from increased winter irrigation, and by increased particulate pollution from urban and industrial sources, agricultural burning and even small heating fires that are lit in response to the fog.  

One of the active partners of the study, Dr Vinayak Sinha, Assistant Professor at the Indian Institute of Science Education and Research Mohali, said the winter fog phenomena is not limited by geographical borders, and to understand it well, scientists of the region need to work together. 

On the side-lines of the Second Workshop on Atmospheric Composition and the Asian Summer Monsoon (ACAM) workshop, a planning meeting on the ‘Multi-country Study of the Persistent Winter Fog over Indo-Gangetic Plain’ was organized by ICIMOD on 7 and 8 June 2015 in Bangkok, Thailand. The meeting brought together atmospheric scientists from ICIMOD’s Regional Member Countries (RMCs) as well as other interested participants. 

The meeting discussed plans for the coming winter, mapping out existing and planned measurement sites, and integration of remote sensing and modelling work with field measurements. Sites across the five countries will be equipped with automated weather stations, aerosol filter samplers, and fog water collectors.  Fog water samples will be analysed for their isotopic composition, allowing for the first ever analysis of the fractional contribution of ground water versus rainfall and surface runoff to fog water across the Indo-Gangetic Plains. Many of the sites will also be equipped with additional instruments that measure gases, aerosols, and atmospheric optical properties. ICIMOD’s Atmosphere Initiative will play a coordinating role and facilitate data sharing and co-authorships.

The Bangkok meeting was attended by scientists from National University of Science and Technology (NUST) and Institute of Space Technology in Pakistan, University of Dhaka and North-South University in Bangladesh, National Environment Commission of Bhutan, Nepal Academy of Science and Technology, the Indian Institutes of Technology in Kanpur and Delhi, the Indian Institute of Tropical Meteorology (IITM), the Indian Institute of Science Education and Research Mohali, the Indian Institute of Science, Aryabhatt Research Institute of Observational Sciences Nainital, Banaras Hindu University, and Dibrugarh University.

After the meeting, Dr Vinayak Sinha said impressive progress has been made given the the various logistical and practical constraints involved in coordinating multiple institutions in five different countries.